NASA scientists reported Nov 4, 2014, on the summary of results from the third year of the Kepler Space Telescope observations. Based on the results from measurements on 40,000 Sun-like stars, Erik Petigura, PhD student at the University of California, Berkeley, Calif. reported that about 22 percent of all sun-like stars should host a roughly earth-size planet in the habitable zone.

The percentage of stars with planets of any size is much larger. Based on the total number of identified stars with planets, William Borucki, Kepler science principal investigator, estimated roughly 70 percent of all sun-like stars in our galaxy may host planets. At the November 4 press conference, he said, "Planets around stars are the norm rather than the exception." He went on to add, "If we ever got star travel, you'd see a lot of traffic jams."

"Since there are about 200 billion stars in our galaxy with 40 billion of them like our Sun," Geoff Marcy, professor of astronomy at UC Berkeley and noted planet hunter said, "that gives us about 8.8 billion Earth-size planets in the Milky Way."

"What this means is, when you look up at the thousands of stars in the night sky," Petigura added, "the nearest sun-like star with an Earth-size planet in the habitable zone is probably only about 12 light years away and can be seen with the naked eye."

The habitable zone is the range of orbital distances from a star that would support liquid water on the planet. For a sun-like star, this is roughly 0.7 to 3 times the Earth's orbit. The habitable zone is sometimes referred to as the "Goldilocks" zone, not too hot, and not too cold.

Since its launch in March, 2009, the Kepler satellite, in a trailing orbit around the sun, has fixed its gaze on a patch of the sky about a hands breath in size, held at arms length. In the field of view of the 95 megapixel camera are over 100,000 stars which Kepler reads every six seconds. The image below shows the area of the sky under Kepler's fixed gaze.

About 5 percent of the pixels record the light intensity of a star and the data is sent back to earth every 30 minutes. With integration times as long as 6.5 hours, the noise floor is about 10 ppm of intensity variability for a 12th magnitude star. The array of 21 active CCD wafers in the focal plane of the telescope is shown in the image below.

This stuff is so exciting! I'm one of those people who firmly believes that, for the survival of the species, we need to be looking at expanding. We need to be moving this direction at a rate much quicker than we currently are. To think there are so many theoretically habitable planets "near by" is exciting, now we just need to figure out the whole... "how do we get there?" issue.

I agree. I've been following this planetary discovery from the start. In large part, because it seemed inconceivable to me that our solar system could be the only one with planets orbiting around its sun.

Perhaps 25 or more years ago now, or shortly before the first non-solar-system planet was discovered, I debated this very point with someone. Although he claimed not to have religious motives, he said "there's no proof of other planets," and concluded therefore that the likelihood was very slim.

Which seems absurd, right? There would be no proof if you didn't have instruments that could detect them. That's a given! But if our sun has planets, how likely is it to be the only sun in 100 billion just in our galaxy alone? I asked him, if you see a coin on the beach under you, do you conclude that most likely, you've found the only coin on all the beaches of the world? Or do you assume that most likely, there are coins hiding on every other beach as well?

Now that we have some rudimentary instruments, lo and behold the most likely truths are being revealed. Not only are there a whole slew of other planets around, but as also might be expected, many of them are roughly in the same size and temperature range as Earth, capable of supporting liquid water, and consequently carbon-based life.

"To think there are so many theoretically habitable planets 'near by' is exciting, now we just need to figure out the whole... 'how do we get there?' issue.

Indeed. We need to discover how to bypass those folds in space, to effectively go faster than the speed of light, without violating any physical laws. Otherwise, even the closest star system, Alpha Centauri, would take amazingly long to reach. Using Voyager's speed, I mean the real one and not the Start Trek one, I think it's something like 17,000 years. Even a super long shot for generation travel, with no oppostunity for resupply.

Keeping in mind that humans have been on this planet for only 40,000 years, out of its 4.5 billion year life, this means that with current technology, it takes almost twice as long as humans have been around, just to reach the CLOSEST other star system.

But the known age of the universe is 13.8 billion years, or 3.1 times longer than the age of Earth. So there's always a potential for some other advanced form of life to be ahead of enough to have beaten this speed barrier somehow.

@Caleb: I'm one of those people who firmly believes that, for the survival of the species, we need to be looking at expanding.

I am 100% with you -- we currently have all of our eggs in one basket (Earth) -- when you think of all the people who have struggled through life to keep the next generation going, it woudl be such a shame to loose it all due to a mega-disaster -- we need outposts on the moon and Mars and then... (I'm channelling Robert Heinlein here :-)

Until not-so-long-ago, if you'd asked me if we were alone in the universe or if there was other intelligent life out thre, I would have replied "there is other intelligent life somewhere" ... but then I read Alone in the Universe by John Gribbin (click here to read my review).

@Caleb, :-) I'm one of those that believes that in the next few million years there is no reason to leave earth if we don't continue to trash it. We've gone from sustainable to unsustainable in around 100 years, and now we're expected to squeeze what little bit of life is left in this planet so that we can spend 36,000 years getting to the next habitable planet only so we can render that uninhabitable within 100 years too. Our problems aren't solved by running away, a lot of the self disipline needed for a reasonable contingent to survive 36000 years in space without self destructing are the same issues we need to survive here for the maybe 1-2 million years we have if we attain that self disipline.

That's not to say that I t think the mind games neeeded study and understand our environment in this manner are misplaced, only that sinking the ship and then leaving it like rats deserting a sinking ship is not the answer.